Windows makes it relatively easy to terminate a program or process which is misbehaving. Just bring up Task Manager and kill it. However, there's much more going on inside your operating system than Task Manager would have you believe. For a truly detailed view, you need a better process manager, and one excellent such program is Process Hacker.
With Process Hacker you can see what's running on your PC, how much resources everything is taking, and much more besides. It's a great way to take a low-level peek into the inner workings of Windows.
Process Hacker requires Windows XP or above, and is less than 1 MB to download. And not only is it free, you can also download the full source code (some 236,000 lines of C) if you really want to get your hands dirty!
Check out http://processhacker.sourceforge.net/ for more details.
My thanks to user "wj32" (the author of Process Hacker) for telling me about this program. If you have a hot find that you want to tell people about, tell me and I'll do the rest. Just see http://www.techsupportalert.com/content/submit-product-review.htm.